Casting mold and basin-like riser therefor

ABSTRACT

In combination with a casting mold there is provided a riser or basin-like funnel communicating with a top region of the mold cavity for after-feed of molten metal to the top region of a solidifying casting; the riser, either open-topped or closedtopped, being shielded against radiant and conduction heat loses by surrounding hollow space and/or thermal radiation or conduction insulating material; also including a knock-off groove-providing formation for riser excess metal resulting on the casting.

United States Patent 1191 Baur [ June 11, 1974 1 CASTING MOLD AND BASIN-LIKE RISER THEREFOR [76] Inventor: Eduard Baur, P.O. Hommerich,

Waldbrugh near Lindlar, Germany 5256 22 Filed: Sept. 12,1972

211 Appl. No.: 287,317

[30] Foreign Application Priority Data Sept. 15, 1971 Germany 2146031 [52] US. Cl. 164/359, 164/360 [51] Int. Cl. B220 9/08 [58] Field of Search 164/122, 125, 359, 360

[56] References Cited UNITED STATES PATENTS 900,970 10/1908 Washburn 164/359 3,120,684 2/1964 Gathmann 164/359 X 3,452,806 7/1969 Wittmoser 164/360 X FOREIGN PATENTS OR APPLICATIONS 272,500 9/1970 U.S.S.R 164/122 1,271,320 6/1968 Germany 164/360 Primary ExaminerJ. Spencer Overholser Assistant ExaminerJohn E. Roethel Attorney, Agent, or FirmPhi1ip D. Golrick 5 7 ABSTRACT 1n combination with a casting mold there is provided a riser or basin-like funnel communicating with a top region of the mold cavity for after-feed of molten metal to the top region of a solidifying casting; the riser, either open-topped or closed-topped, being shielded against radiant and conduction heat loses by surrounding hollow space and/or thermal radiation or conduction insulating material; also including a knock-off groove-providing formation for riser excess metal resulting on the casting.

28 Claims, 19 Drawing Figures \(l/l/I/[Ill CASTING MOLD AND BASIN-LIKE RISER THEREFOR The present invention is concerned with a casting mold in combination with a basin-like funnel serving as a riser (feeder or header) therefor and comprised of a material resistant to the molten metal, providing for an after-feed of molten metal to and during solidification of the metal casting. Such a riser provides a space into which poured metal rises after at least substantially filling the mold casting shape determining main cavity, thus affording a reservoir back-feeding additional molten metal to the casting as it solidifies in the mold thereby preventing in the casting a shrinkage cavity or pipe.

The prior art has provided so-called insulating risers, headers, heads or funnels the purpose of which is to diminish heat transmission to the environment, from the molten metal in the riser, thereby maintaining the melt in the funnel hot for a long period and also, in a net result, enabling diminishing the riser volume. Hitherto large wall thicknesses have been used in such insulating funnels or risers, with a correspondingly high insulation material requirement.

The broad object of the present invention is to provide an improved basin-like funnel or riser of greater insulating ability for casting molds, especially for steelcasting, which at the same time is not fragile, but is rather quite resistant to breakage in transporation.

For this purpose, by the present invention, a casting mold is made with a built-in basin-like funnel or riser having, at least after metal has been poured therein, an insulating space between the surrounding molding sand composition and the outer wall surface of the riser, the latter being comprised of a refractory material resistant to the'cast molten metal. This insulating space affords a greater heat insulation effect, so that a metalreceiving riser structure, comprised of insulating material, can be comparatively quite thin-walled, or even with thin-walled construction, can be comprised of a material which itself offers only slight thermal insulation or no better insulation than the associated molding composition. The riser .unit or assembly to be incorporated in the mold includes structure resulting in a riser basin which, after metal pouring, is appropriately supported in the, mold with an insulating hollow or air space between at least a portion of the basin outer surface and adjacent molding composition comprising the mold.

A refractory structure providing the basin-like riser has projections whereby the basin may be supported in a preformed recess in the molding sand composition in the mold box, with the basin surface to be insulated spaced from the recess face to form an air space; or the basin surface may be surrounded or covered by a jacket element forming an insulating space free of the molding composition. Such a jacket element can be a shell comprised of paste board attached to, and spaced from the outer surface of, the basin. Or the jacketing element may be comprised of a foam plastic applied to the basin area to be insulated, especially an area to be insulated by a hollow space arising upon thermal decomposition or gasification of the jacket material upon filling of the mold with and rising of moltenmetal into the basin.

Moreover, the riser basin itself may be comprised of a material of rather slight heat conductivity and having cavities distributed therethrough, particularly produced by expanded granules of the mineral perlite. Preferably the basin is thin-walled and highly refractory material, here to be understood as a material having a melting point higher than 1,600 C.

Particularly advantageously the basin is made of highly refractory mineral fibers, for example, fibers of Kaolin, quartz glass, especially advantageously magnesia (magnesium oxide), or fibers of burned magnesite. The latter advantageously has a melting point exceeding 2,400C. and with application of higher pressures of from 200 to 800 kp/cm. is compressed to a comparatively thin walled highly refractory vessel.

Therewith arises a further advantage that with application of the high compression pressures, through press or vibration action, a chemical bonding is possible by the Sorel process, conferring a high rigidity and stability upon the press formed element.

Under the later influence of the high temperatureof the molten cast metal, e.g., from l,200 to l,600C this initial chemical bonding then is terminated and succeeded by a ceramic type bonding, so that contrary to what has been the case with insulated funnels hitherto, a premature burning out and consequent destruction of the riser does not occur.

Accordingly insulating funnels comprised of highly refractoryv mineral fibers can be fabricated in a very thin wall form, so that the material requirement is extremely small. I

In combination with the thin wall of the riser basin particularly of the described fibrous magnesite composition, especially advantageously the exterior surface has a radiation diminishing jacket or layer, which has as its principal component, preferably-grey-oxidized lead and/or zinc and/or bismuth, all materials having a very slow thermal radiation coefficient or character.

With one form, this thin walled refractory basin has unitary, integrally formed outwardly extending projections, flanges or like spacing support means engaged in or on the molding sand composition of the casting mold. Where the basin is set into an appropriate larger dimensioned previously prepared mold recess, between the principal external basin surface and the casting mold material there results a hollow space which greatly increases the insulating effect, by virtue of the very slightthermal conductivity of the air enclosed therein. This construction is advantageous not only with a basin material of conventional conductivity, but also where a material of low heat conductivity is used such as the above mentioned fibrous burned magnesite.

in such case, for its support the basin has such projecting support means at least at its upper region. But with the aforementioned spacing supports provided by circumferential flanges'at both the top and bottom ends of the basin, the annularly shaped air space between the basinand surrounding material of the casting mold is closed off to minimize air circulation as far as possible.

By a further modification the foam plastic jacket is terminated at a spacing from the bottomend of the basm.

The inventive concepts are applicable for open and also closed riser basins. in the latter case, the closed basin may have a rather rough ball-like form of construction; and to this purpose comprises a. primary basin bottom part and a capping top part, in a throughaperture of the latter of which there is disposed a gaspermeable truncate Conical shaped core, likewise serving as a spacing support element for the basin, engaged in the casting mold body at a location spaced from the basin top.

Moreover, by a further modification, a foamed plastic jacket is provided comprised of or incorporating material exothermically reacting in the decomposition of the foam plastic under casting temperature, and such that there is obtained a heating of the molten metal in the basin without the metal being otherwise affected through the exothermic action and without undesired material passing into the melt. This expedient is especially advantageously used with a thin-walled basin, where in consequence of the slight wall thickness, good heat transmission occurs.

For manufacture of basin jacketing of this type from foam plastic, a long tube of foamed plastic may be made of appropriate shape having external circumferential grooves at spacings longitudinally which correspond .to the length of the jacket elements.

The invention is hereinafter explained in further detail relative to the drawings, but is not limited to the specific embodiments there represented.

Other objects and advantages will appear from the following description and the drawings wherein:

FIG. 1 is a vertical section through a casting mold incorporating an insulated riser basin representative of the prior art;

FIG. 2 is a vertical section, similar to FIG. 1, through v a casting mold with a riser basin; I

v FIG. 3 is a vertical axial section through a basin per se and of modified form;

FIG. 4 is a top plan view corresponding to FIG. 3;

FIG. 5 is a vertical section through a fragmentarily shown casting mold and through of a therein incorporated basin similar to that of FIG. 3 with slight modification;

FIG. 6 is a vertical section which relates to furthe modification of the riser basin unit;

,FIG. 6a is a vertical section which relates to further modification of the riser basin unit;

I FIG. 7 again is a vertical section through a portion of a casting mold having incorporated therein a riser basin unit of FIG. 6;

FIG. 7a again is a. vertical section through a portion of a casting mold having incorporated therein a riser basin unit of FIG. 6a;

FIG. 8 is a vertical section through a somewhat ballshaped riser basin unit modification, presenting a closed top type riser;

FIG. 9 is a vertical section through part of a casting a mold and of a therein incorporated riser basin from FIG. 8;

FIG. 10 is a vertical section through a tube of foamed plastic sub-divisible into riser basin surrounding jacket elements; I

FIG. 11 is a fragmentary view partially in vertical section of a modified riser basin unit;

FIG. 12 is a-fragmentary vertical section through a casting mold, with a basin incorporated therein generally of the form of that shown in FIG. 6;

FIG. 13 is a vertical section through a riser basin unit as a modification of a cylindrical form, which also may provide the basic components for more complex forms;

FIG. 14 is a vertical section through a still further modification of the riser basin unit;

FIG. 15 is a vertical section through a still further cylindrical riser basin unit modification of open top form;

FIG. l6is a fragmentary vertical section through a top or copepart of a casting mold having incorporated therein a riser basin unit somewhat similar to that of FIG. 15 with still further modification; and

FIG. 17 is a vertical section similar to that of FIG. 16, but showing a still further modification of the riser basin unit shown in FIG. 16, and presenting a closed top type basin.

PRIOR ART FIG. I

For comparison purposes, an example of prior art practice is represented in the vertical section of FIG. 1

through a foundry mold flask, comprised of upper and lower portions,,cope 11 and drag l0, clamped together to bring into proper relation and alignment the mold cavity 12 for the casting to be produced, respective parts of the gate-sprue system 13, 13a, the metal receiving space 14 being defined by-a surrounding usually cylindrical riser basin element 15, as severally formed in the molding sand composition 16 contained in the cope and drag. a

\ For simplicity of representation and discussion, the cavity 12 is shown as essentially rectangular in shape for producing a corresponding block shaped casting. The cylindrical more or less refractorybasin element 15 defines a riser space extending fromthe top of the casting determining mold cavity 12 upwardly through the thickness of the molding sand compositionin the cope, providing a reservoir into which the molten cast metal, poured into sprue 13a, rises after filling the cavity 12. The molten metal in the riser space thus supplies molten metal from above the mold cavity and to the central region of the casting being produced as it is solidifying thereby to obviate any shrinkage cavity, a center hollow termed a pipe, which might otherwise arise. This of course usuallyresults in more or less waste metal on the top of the casting at the location of the riser space, later to be removed as waste metal, such waste or excess also generally termed the riser.

" FIG. 2

preferred feature of the present invention the basin l5 at its bottom region is inwardly fianged at 17 forming a' central constriction or in effect an apertured basin bottom wall, the bottom or flat lowerface 18 of which coincides with the molding flask'parting plane, and also top of the cavity 12; the restricted opening 19, here shown round, having inwardly beveled top and bottom margins 20, 20 giving' a'wedge shaped radial crosssection at the opening edge to serve in a sense as a core forming a corresponding sectioned weakening groove beneath the riser waste metal on the casting facilitating knock-off or removal of the waste after or possibly even during shake out from the mold. For the moldriser arrangement as shown in FIG. 2, thebasin -like riser 15 may be comprised of a refractory and insulating material as hereinafter described with respect to other FIGURES, e.g., a porous material of small heat conductivity, especially comprised of hollow or expanded granules of the mineral perlite embedded in a sand composition cold bonded by a synthetic resin binder; and thiswithout more may provide a riser basin unit incorporated in the cope section of the mold.

RISER BASIN In FIG. 3, the riser basin unit to be incorporated in the mold includes the riser basin l5 and a jacket element or mantle 21. The riser proper is comprised of a highly refractory material which is made from a fibrous material such as fibrous fired magnesite, which by virtue of its magnesium oxide content, results in a melting point exceeding 2,400C and has a low heat conductivity. The fibrous form of such material is especially suitable as enabling the fabrication of extremely thin walled basins without danger of crack formation, by application of high press forming pressures.

An improved riser insulating effect is obtained by making the jacket element 21 of thermally destructible foam plastic, which not only spaces the basin from surrounding molding sand composition rammed into the mold flask in which the unit is emplaced, but also, either in the firing or bake-out of a dry sand mold or by the heat of the metal poured into say a green sand mold and rising in the basin 15, the plastic foam material is gasified, forming as appears in FIG. 5, for a slightly modified basin 15, the annular air gap hollow space 23, between the external circumferential surface of the basin and surrounding molding sand 16. The insulating air space 23 is represented in FIG. 5 as it would appear after gasification of jacket 21, even though a wood block pattern is shown in the bottom of the flask to show its basin unit supporting relation as at the stage when the cope has just been completely rammed with sand.

Preferably the basin conical exterior in FIG. 3 has nesting-contact-limiting integral projections 26, for example, circumferentially continuous ribs or beads, vertically longitudinally running ribs or merely local bosses, so that units vertically nested and stacked for secure transport can yet be readily separated.

Accordinglyto support the basin in the mold outward of the gap after gasification of the plastic foam, at its upper end it is fabricated with integral horizontally outwardly extending projection means, such as the circumferential flange or rim 24, in the unit or assembly of basin and collar jacket to engage circumferentially edgewise against, and also rest on a resulting ledge beneath its outer margin in, the surrounding molding sand. The flange has a plurality of spaced edge notches extending radially in to overlap the collar top edge thereby to afford vents for escape of gases generated by the thermal decomposition of the foam. Preferably as shown in FIG. 3, the bottom margin of the foam jacket is beveled to afford first better sand packing inward, supporting the unit, further preferably with the collar terminating short of the end, affording supporting sand contact for the lower region of the basin, whether the basin side continue cylindrical or (as in FIG. 5)of one conical slope to the bottom, or whether, as in FIG. 3, the bottom outer edge of the basin be also beveled so that a higher degree of under-support is offered in addition to a lateral support component.

Also in FIG. 5, on the major external surface of the basin 15 proper, there is shown a heat radiation minimizing layer 38, particularly advantageously comprised of oxidized lead, zinc, or bismuth, because these materials have a very small heat radiating ability.

FIGS. 6 7a In FIG. 6, there appears a thin walled basin 15 comprised of the herein described magnesite fiber composi tion, again of a basically truncated conical form, but at both the upper and lower ends having integral radially outwardly extending continuous circumferential flanges 35 and 36 respectively.

With the mere basin 15 of FIG. 6 as the unit going into a mold, the hollow space 23 can be attained by first providing in the mold sand an appropriate truncated conical cavity, into which the FIG. 6 basin is then set, resulting immediately in the structure of FIG. 7; the flanges 35 and 36 thus being supported by the surface of the appropriately shaped correspondingly dimensioned internal conical surfaces of the recess thus preformed in the sand. However, the basin form of FIG. 6 may be a component of a more complex unit not requiring a pre-formed recess as later noted.

In the unit modification of FIG. 6a, the basin 15 lacks the bottom flange, but provides a surrounding hollow truncated conical thin walled jacket or shell 37 with its upper edge circumferentially engaging orattached to basin flange 35, and at its bottom end having an inwardly turned flange engaging the unflanged bottom external circumference of the basin 15. Shell jacket 37 preferably for low cost is made of pasteboard, for example, treated at its lower end at least to withstand crumbling after pour, until the metal surface therebeneath solidifies and hence cannot rise in space 23; and thus to afford a substitute for the previously described foam plastic or jackets, for forming the hollow space 23 as in FIG. 7a when the riser basin assembly or unit is incorporated in the mold with sand compacted thereabout as previously described. A similar simple paste board shell located between flanges 35, 36 of the FIG.

6 basin (or foam therebetween) enables use of that basin form in a unit incorporated in the mold as the sand is compacted into the cope.

FIGS. 8 9; CLOSED RISER also a central top opening or aperture 15p; the upper jacket 21a having a recess or gap 28, not only providing an aperture portion in alignment with cap aperture 15p, but also laterally thereof a further space providing access of molding sand from the main surrounding molding composition sand body to form a sand bridge for supporting and holding the basin parts after gasification of the foam material.

In place of and preferably in addition to such sand bridge support, as shownin FIG. 9, support can be provided by a truncated conical gas permeable plug-like element 29; which to provide a high rigidity, advantageously is comprised of porcelain. The plug preferably has an axial through-passage 30 as a gas discharge vent, with a further passage 31 running laterally outwardly to open into the hollow space 23 formed upon gasification of the plastic.

The closed top embodiment of FIGS. 8 and 9 affords an especially high insulating capacity because thermal loss upwardly is to a great degree impeded.

FIG. 10 shows a system for production of the foam jackets 21 such as used in various of the aforegoing units, several jackets being, as it were, simultaneously foamed, or produced connected together endwise in a somewhat tube-like form, an advantageous stock form for storage until needed; the tube being subsequently sub-divided into the individual jacket elements. Preferably to facilitate the division, at appropriate locations for the individual lengths, perhaps as foamed or by a subsequent operation, the tube is provided with weakening grooves or notches as 39-40, enabling easy cutoff or even a simple break-off, fairly readily and reliably obtained, of the successive sections from the tube length. I

FIGS. 11 12 LATERAL BACK FEED In FIG. 11 appears a riser basin unit having a markedly different configuration from others, herein discussed with, moreover, only a portion of the basin external surfaces jacketed by the foamed plastic 21. This arrangement is adapted, e.g., for incorporation in a mold (see FIG. 12) producing a casting having a vertically extending thinner section formed in the mold cavity upper part 12a, to one side of which, with vertical overlap and lateral communication, the riser 15 is lo- I cated.

. The basin over its major length has a hollow or square tubular horizontal cross section, with the wall adjacent the cavity portion 12a including at its bottom the constricted opening 19 flanged outwardly to meet the cavity; the opposite basin wall merging into a bottom curving down to opening 19. The flanging and the beveled edge of the aperture here again provide a knock-off groove forming core. The basin 15 is not jacketed with the foam plastic on this apertured side, nor in the region below and near the aperture formation, but rather only towards the outer side of the flask, preventing heat loss from the riser to any great extent in those directions, while permitting a heat transmission inwardly toward the top thin mold cavity section 12a, whichvis. not only acceptable but even desirable to aid better cavity fill and maintaining soundness of metal there.

FIG. 11 also shows a point of advantageous structure in the unit, particularly in the jasket which may be useful to avoid need for support structures such as the projecting rim 24 in FIGS. 3-5 and other prior figures;

namely, the provision of one or more recesses in the foam layer 21 extending into the basin itself, for example, as shown in the top region at 27. Upon incorporation of the unit in the flask, compacted sand extends from the main sand mass or body into the basin thus forming one or more supporting bridges 27b spanning the gap formed upon gasification of the foam. Of course, a similar expedient could be used with the more or less truncated conical basin form, e.g., as represented in FIGS. 3-5, so that the rim or flange 24 could be there eliminated.

FIGS. 13 14 NO CONSTRICTION FIG. 13 shows a simple cylindrical basin unit which in one respect discloses a variation for structure basically common to subsequent figures. About the refractory simple cylindrical basin 15, adapted for extrusion production with suitable material, there is also here provided a fitted, bonded or otherwise attached surrounding foamed plastic jacket 21, as and for the purposes previously described, terminating short of both top and bottom ends of hollow cylinder 15, and with bottom end preferably beveled as shown, affording regions for supporting circumferential engagement by the mold sand when used as a total riser basin unit going into a mold, or other uses when incorporated in a more complex unit. The inner refractory cylinder may be comprised of two endwise abutting shorter lengths, as 15a, 15b in FIG. 14, held together as a unit for incorporation into a mold by the jacket 21.

The composition used for cylinder 15 may comprise a high proportion of granules 32 of expanded perlite distributed in a matrix of a molding sand composition constituted mainly of quartz sand, say of particle size H 32, with a cold hardening synthetic resin binder.

By virtue of large volume, that is, low density, and by their internal cavities, the perlite granules both reduce basin weight and increase the insulating value of the resulting structure.

In FIG. 14, the basic structure of FIG. 13, with the basin provided by two shorter cylindrical parts 15al5b butted and held by plastic foam jacket 21 (previously described as alternative to a single unitary cylinder), is incorporated in a closed top type basin unit. This unit includes, inserted in the top end of cylindrical basin portion 15a, a centrally apertured closure plate or disk 34, cemented or otherwise coaxially bonded to a circumferentially downwardly cylindrically flanged paste board disk 33 fitted over the top end of 15a; here again gas permeable plug 29, similar to that described and shown in FIG. 9, being provided for like purposes of venting and also support of the unit and final basin structure in the mold sand body. Closure plate 34 may have the same composition as the basin element 15; may be further bonded to 15 (or 15a) with 33 serving initially as a support therefor in manufacture; and also where particular pouring and molding conditions permit, may be comprised of synthetic -plastic foam with expanded perlite granules distributed therein. A bottom constriction as in FIG. 16 may be added.

It may be here observed that manufacture of the riser basin elements from Kaolin fibers or magnesite fibers has the advantage that these fibers are chemically bonded, for form retention by a cold (i.e., non-heated) procedure by use of a high compression pressure for example, through use of an acid aluminum phosphate binder; but upon heating by the molten metal pour this chemical bond is converted into a highly refractory ceramic binding through melting of the silicaceous components.

FIGS. 15 17 FIG. 15 shows in cross section a riser basin unit including a cylindrical basin element 15 comprised of fired clay or like refractory with distributed mineral fiber inclusions 41 to achieve a high strength and rigidity with small wall thickness, counteracting tendency to split under thermal shock; and also a surrounding cylindrical jacket element 21 comprised of expanded perlite granules 42 distributed in a foamed plastic matrix reducing the jacket weight. This structure may, of course,

be used with ancillary bottom and top elements as described relative to FIGS. 16-17.

In the unit of FIG. 16, the cylindrical riser basin element is comprised again of fired clay or like refractory material, preferably with reinforcing mineral fiber inclusions 41, and further a multiplicity of distributed tiny plastic foam spheres or tiny hollow plastic balls 43 providing hollow spaces or cavities.

In consequence of these numerous spaces or cavities, advantageously the riser 15 has a very light weight and even by their very presence alone offers a comparatively good thermal insulating performance in the riser, quite apart from any surrounding air space that may develop in the mold environment, so that this riser basin 15 may be used alone as in FIG. 2. The numerous cavities, furthermore, impede splitting of the funnel upon the sudden heating resulting upon pouring of the mold, in this cooperating with the mineral fibers 41. To the extent that these porous or hollow plastic inclusions are gasified by the heat of poured metal, the insulation effect of the riser may be further increased. However, if preferred for further safety, wire 49 may be wound on the exterior of 15 (and so also for other basin forms) whereby in the event of cracking, the pieces are held together to render the crack relatively harmless.

The basin 15 in the unit of FIG. 16 likewise is surrounded by a foam plastic sleeve jacket 21 and a jacket top end overlaying flat insulating ring 50, e. g., of asbestos; while at its bottom end there is an annular element 44 again providing a core at constricted opening 19 for forming a riser metal break-off groove. This element 44 also has first an integral, preferably annular, upwardly extending inner flange 45 bonded to the bottom margin of the inner surface of the basin 15 preferably by cementing. The element 44 extends radially beyond the jacket 21, to prevent relative dislodgement of the basin, and has a second vertically directed collar flange 44a from which extends horizontally a circumferential flange 44b, to be anchored in the body of the molding sand composition of the mold in which the unit is incorporated. However, the flanges 44a and 44b do not have to be circumferentially continuous to provide the unit support and ultimate riser basin support in the mold.

The break-off core element 44 is preferably comprised of such material that it also burns out after the pouring and metal solidification.

The plastic foam jacket 21 of FIG. 16 (also of FIG. 17 to be described) likewise can contain distributed granular expanded perlite.

This annular flat plate 50 further gives a top closure so that air cannotcirculate in and out of the hollow space between the molding sand body and the basin by the burn-out of thefoam plastic; and this ring plate 50 further supports the top of the basin 15 laterally on the molding sand composition.

The unit of FIG. 17 adds top closure structure to what is basically the construction of FIG. 16 with the exception, that its flat annular bottom element 44x is not designed as a break-off groove forming core. The bottom element 44x has the upwardly projecting means 45a, here again an annular flange, with which the cylindrical riser basin element 15 is connected by cementing to avoid displacement, located externally of the basin bottom margin; and again its material is selected to be inert to and have no adverse effect upon the casting. The circumferential radial projection of the element 44x beyond the jacket 21 also engages surrounding mold sand to support against displacement.

The disk-like cover plate 46, similar in composition to basin 15 and over-laid by a preferably cemented-on disk plate 47 of the plastic foam, has a downward coaxial annular flange 48 projecting into, and centering it on, the top of riser 15, preferably cemented therewith.

The arrangement and construction of FIG. 17 has the advantage that when embedded in the molding sand composition 16, there are no notable heat transmission bridges from the basin to the molding sand composition. Particularly, as a closed top form entirely surrounded and covered by the mold sand fill, the hollow resulting upon gasification of foam plate 47 minimizes upward conductive losses from the cover.

The units of FIGS. 16 and 17 have the advantage that the riser basins proper, even in themselves, have an extremely low heat conductivity, and are comprised of such material as permits economic low cost fabrication and is inactive relative to the molten metal. The essential insulation performance is attained through the hollow space arising after the burning out of the foam plastic mantle 21.

The units of FIGS. 16 or 17 are accordingly essentially comprised of three conjoined elements, each designed according to its respective allotted function; the basin 15 to be comparatively unreactive with the molten metal; the jacket 21 providing the essential insulating space; and the break-off core 44 preferably burning out after the pouring is completed and the casting at least solidified.

In the aforegoing description, various structures and shape of riser units are disclosed whichnot. only show adaptability of the invention to distinct mold and casting requirements, but also forms suitable to different fabricating techniques such as molding, or extrusion,

for the production of the refractory riser; also diverse materials and fabrication for the jacket, such as foaming in place, production of multiple length stock pieces, or fitting and cementing in place on individual basins, and even the possibility of foaming in place on long length extrusions of basin material to be later cut to length.

The light weight compositions for basins and/or jackets not only conduce to material savings or better insulating character, but also to simplicity of supporting engagement with the molding sand composition.

Also the strength of the basin compositions, especially with fibrous incorporations or external wire winding, reduces not only unacceptable damage by thermal shock, but also minimizes damage in handling and transport of the units, to which latter function even the foam jackets contribute.

What is claimed is:

1. For incorporation in the body of molding sand or like molding composition in a casting mold with a builtin riser, a riser basin unit comprising:

a basin-like component providing a riser basin of a material capable of withstanding the molten metal to be cast; and

means cooperating with surrounding molding composition in a mold to define an insulating space between the molding composition body of the mold and an outer wall surface portion of the basin at least after metal has been poured into the mold;

said means comprising a jacket element spacing molding composition from said outer wall surface portion when said unit is incorporated in a mold for forming an insulating hollow space.

2. A riser basin unit as described in claim 1, wherein said jacket element is comprised of foamed plastic gasifiable at a temperature below a pouring temperature of the metal to be cast.

3. A riser basin unit as described in claim 1, wherein the jacket element is comprised of expanded, granular perlite mineral embedded in foamed plastic as a matrix.

4. A riser basin unit as described in claim 2, wherein the foamed plastic element comprises a circumferentially continuous collar and, at the bottom end region of the riser basin, has a beveled end.

5. A riser basin unit as described in claim 1, wherein the riser basin is comprised of expanded granules of the mineral perlite, embedded in a synthetic resin bonded sand matrix.

6. A riser basin unit as described in claim 1, wherein the riser basin is comprised of mineral fibers, particularly fibrous Kaolin or magnesite, for shape retention, having a bonding which is initially chemical and becoming ceramic under the heat of the cast metal.

7. A riser basin unit as described in claim 1, wherein the riser basin is comprised of a thin-walled refractory ceramic material.

8. A riser-basin unit as described in claim 7, wherein said ceramic material is clay and has numerous small cavities distributed therethrough.

9. A riser basin unit as described in claim 8, wherein a multiplicity of hollow cavities is obtained in the basin through plastic foam spheres or granules distributed throughout the clay and gasified upon high heating of the basin.

10. A riser basin unit as described in claim 9, wherein said basin has mineral fibers embedded therein.

11. A riser basin unit as described in claim 9, wherein said basin comprises a cylindrical extrusion.

12. A riser basin unit as described in claim 1, including a bottom end element providing a feed metal knock-off forming constriction and an integral collar circumferentially engaging a cylindrically shaped bottom end portion of said basin.

13. A riser basin unit as described in claim 1, including a cover of refractory material for the top of said basin, and an overlay of plastic foam on a substantial portion of the outer surface of said cover.

14. A riser basin unit as described in claim 1, wherein said riser basin is provided with unitary externally extending projection means engageable with the body of the molding composition of the casting mold and thus affording basin spacing support means.

15. A riser basin unit as described in claim 14, wherein spacing support means are present on both the top and bottom ends of said riser basin.

16. A riser basin unit as described in claim 1, wherein said jacket element is a collar comprised of expanded perlite granules bonded together or embedded in a plastic foam matrix, and

said riser basin is provided by a refractory and loadable layer on at least the inner circumferential surface of said collar.

17. A riser basin unit as described in claim 1, wherein said riser basin has a closed topped construction.

18. A riser basin unit as described in claim 17, wherein said riser basin is comprised of a downwardly diminishing truncated conical bottom part and a top part capping said bottom part,

'said top part having an upwardly open aperture therethrough, and including a truncated conical permeable vent element inserted in said aperture and projecting upwardly therefrom to afford, as a support element for the basin, engagement at a spacing from the basin in the molding composition.

19. A riser basin unit as described in claim 1, wherein the external surface of the riser basin has a radiation diminishing covering.

20. A riser basin unit as described in claim 19, wherein the radiation diminishing covering is comprised of oxidized lead, zinc or bismuth.

21. A riser basin unit as described in claim 2, wherein the jacketing of synthetic plastic foam is provided by a substance exothermically reacting upon the burning of the plastic foam.

22. A riser basin unit as described in claim 1, wherein said riser basin is comprised of two vertically aligned endwise abutting hollow parts, and

said jacket element comprises a synthetic foamed plastic sleeve embracing and holding said hollow parts together.

23. For use as foamed plastic jacket elements in riser basin units as described in claim 1, along tube of foamed plastic of length equal to a multiple greater than three time the height of a said jacket element, and having at spacings, corresponding to the height of the jacket elements, exterior circumferential grooves facilitating division of the tube into individual jacket elements.

24. A riser basin unit as described in claim 12, wherein said bottom end element has an external upwardly projecting collar.

25. A riser basin unit as described in claim 1, wherein said jacket element is a foamed plastic sleeve embracing said riser basin, and including an insulating ring covering the top of said sleeve. 26. A riser basin unit as described in claim 1, wherein said riser basin has a hollow cylindrical construction with a wire winding externally on a cylindrical surface.

27. A riser basin unit as described in claim 1, wherein said jacket element comprises a paper-board shell including a major portion with an outward spacing from the external surface of said riser basin,

at least one of said basin and said shell having portions projecting toward the other to maintain said outward spacing, and defining with said major portion a space wherein said molding composition is spaced from regions of the basin to be insulated, thereby to define an insulating air space.

28. A riser basin unit as described in claim 1, wherein said riser basin comprises an annular solid of revolution, having a top opening and a bottom opening, and

said jacket element comprises a shell circumferentially embracing said solid over a principal part of its length. 

1. For incorporation in the body of molding sand or like molding composition in a casting mold with a built-in riser, a riser basin unit comprising: a basin-like component providing a riser basin of a material capable of withstanding the molten metal to be cast; and means cooperating with surrounding molding composition in a mold to define an insulating space between the molding composition body of the mold and an outer wall surface portion of the basin at least after metal has been poured into the mold; said means comprising a jacket element spacing molding composition from said outer wall surface portion when said unit is incorporated in a mold for forming an insulating hollow space.
 2. A riser basin unit as described in claim 1, wherein said jacket element is comprised of foamed plastic gasifiable at a temperature below a pouring temperature of the metal to be cast.
 3. A riser basin unit as described in claim 1, wherein the jacket element is comprised of expanded, granular perlite mineral embedded in foamed plastic as a matrix.
 4. A riser basin unit as described in claim 2, wherein the foamed plastic element comprises a circumferentially continuous collar and, at the bottom end region of the riser basin, has a beveled end.
 5. A riser basin unit as described in claim 1, wherein the riser basin is comprised of expanded granules of the mineral perlite, embedded in a synthetic resin bonded sand matrix.
 6. A riser basin unit as described in claim 1, wherein the riser basin is comprised of mineral fibers, particularly fibrous Kaolin or magnesite, for shape retention, having a bonding which is initially chemical and becoming ceramic under the heat of the cast metal.
 7. A riser basin unit as described in claim 1, wherein the riser basin is comprIsed of a thin-walled refractory ceramic material.
 8. A riser basin unit as described in claim 7, wherein said ceramic material is clay and has numerous small cavities distributed therethrough.
 9. A riser basin unit as described in claim 8, wherein a multiplicity of hollow cavities is obtained in the basin through plastic foam spheres or granules distributed throughout the clay and gasified upon high heating of the basin.
 10. A riser basin unit as described in claim 9, wherein said basin has mineral fibers embedded therein.
 11. A riser basin unit as described in claim 9, wherein said basin comprises a cylindrical extrusion.
 12. A riser basin unit as described in claim 1, including a bottom end element providing a feed metal knock-off forming constriction and an integral collar circumferentially engaging a cylindrically shaped bottom end portion of said basin.
 13. A riser basin unit as described in claim 1, including a cover of refractory material for the top of said basin, and an overlay of plastic foam on a substantial portion of the outer surface of said cover.
 14. A riser basin unit as described in claim 1, wherein said riser basin is provided with unitary externally extending projection means engageable with the body of the molding composition of the casting mold and thus affording basin spacing support means.
 15. A riser basin unit as described in claim 14, wherein spacing support means are present on both the top and bottom ends of said riser basin.
 16. A riser basin unit as described in claim 1, wherein said jacket element is a collar comprised of expanded perlite granules bonded together or embedded in a plastic foam matrix, and said riser basin is provided by a refractory and loadable layer on at least the inner circumferential surface of said collar.
 17. A riser basin unit as described in claim 1, wherein said riser basin has a closed topped construction.
 18. A riser basin unit as described in claim 17, wherein said riser basin is comprised of a downwardly diminishing truncated conical bottom part and a top part capping said bottom part, said top part having an upwardly open aperture therethrough, and including a truncated conical permeable vent element inserted in said aperture and projecting upwardly therefrom to afford, as a support element for the basin, engagement at a spacing from the basin in the molding composition.
 19. A riser basin unit as described in claim 1, wherein the external surface of the riser basin has a radiation diminishing covering.
 20. A riser basin unit as described in claim 19, wherein the radiation diminishing covering is comprised of oxidized lead, zinc or bismuth.
 21. A riser basin unit as described in claim 2, wherein the jacketing of synthetic plastic foam is provided by a substance exothermically reacting upon the burning of the plastic foam.
 22. A riser basin unit as described in claim 1, wherein said riser basin is comprised of two vertically aligned endwise abutting hollow parts, and said jacket element comprises a synthetic foamed plastic sleeve embracing and holding said hollow parts together.
 23. For use as foamed plastic jacket elements in riser basin units as described in claim 1, a long tube of foamed plastic of length equal to a multiple greater than three time the height of a said jacket element, and having at spacings, corresponding to the height of the jacket elements, exterior circumferential grooves facilitating division of the tube into individual jacket elements.
 24. A riser basin unit as described in claim 12, wherein said bottom end element has an external upwardly projecting collar.
 25. A riser basin unit as described in claim 1, wherein said jacket element is a foamed plastic sleeve embracing said riser basin, and including an insulating ring covering the top of said sleeve.
 26. A riser basin unit as described in claim 1, wherein said riser basin has a hollow cylindrical construction with a wire winding exTernally on a cylindrical surface.
 27. A riser basin unit as described in claim 1, wherein said jacket element comprises a paper-board shell including a major portion with an outward spacing from the external surface of said riser basin, at least one of said basin and said shell having portions projecting toward the other to maintain said outward spacing, and defining with said major portion a space wherein said molding composition is spaced from regions of the basin to be insulated, thereby to define an insulating air space.
 28. A riser basin unit as described in claim 1, wherein said riser basin comprises an annular solid of revolution, having a top opening and a bottom opening, and said jacket element comprises a shell circumferentially embracing said solid over a principal part of its length. 